MallocSiteHashOverflow.java

/*
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/*
 * @test
 * @summary Test corner case that overflows malloc site hashtable bucket
 * @requires sun.arch.data.model == "32"
 * @key nmt jcmd stress
 * @library /testlibrary /testlibrary/whitebox
 * @build MallocSiteHashOverflow
 * @run main ClassFileInstaller sun.hotspot.WhiteBox
 * @run main/othervm -Xbootclasspath/a:. -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI -XX:NativeMemoryTracking=detail MallocSiteHashOverflow
 */

import com.oracle.java.testlibrary.*;
import sun.hotspot.WhiteBox;

public class MallocSiteHashOverflow {

    public static void main(String args[]) throws Exception {

        // Size of entries based on malloc tracking header defined in mallocTracker.hpp
        // For 32-bit systems, create 257 malloc sites with the same hash bucket to overflow a hash bucket
        long entries = 257;

        OutputAnalyzer output;
        WhiteBox wb = WhiteBox.getWhiteBox();
        int MAX_HASH_SIZE = wb.NMTGetHashSize();

        // Grab my own PID
        String pid = Integer.toString(ProcessTools.getProcessId());
        ProcessBuilder pb = new ProcessBuilder();

        // Verify that current tracking level is "detail"
        pb.command(new String[] { JDKToolFinder.getJDKTool("jcmd"), pid, "VM.native_memory", "statistics"});
        output = new OutputAnalyzer(pb.start());
        output.shouldContain("Native Memory Tracking Statistics");

        // Attempt to cause NMT to downgrade tracking level by allocating small amounts
        // of memory with random pseudo call stack
        int pc = 1;
        for (int i = 0; i < entries; i++) {
            long addr = wb.NMTMallocWithPseudoStack(1, pc);
            if (addr == 0) {
                throw new RuntimeException("NMTMallocWithPseudoStack: out of memory");
            }
            // We free memory here since it doesn't affect pseudo malloc alloc site hash table entries
            wb.NMTFree(addr);
            pc += MAX_HASH_SIZE;
            if (i == entries) {
                // Verify that tracking has been downgraded
                pb.command(new String[] { JDKToolFinder.getJDKTool("jcmd"), pid, "VM.native_memory", "statistics"});
                output = new OutputAnalyzer(pb.start());
                output.shouldContain("Tracking level has been downgraded due to lack of resources");
            }
        }
    }
}